I think it is down to if the Council inspects a property that is found to be in substantial disrepair they may serve a notice on the person having control of the property, e.g. the landlord. Things that would constitute disrepair are:
A hole in the roof, perhaps a slipped slate
Rotten window frames
Leaking gutters
Cracked render
Crumbling brickwork
Perished or crumbling wall plaster
but each coucnil may have their own interpretation.
Hope this helps
Russell